This application relates to the field of door access security systems and, particularly, to the field of card readers for door access security systems.
Door access security systems, utilizing magnetic card readers at doors to be controlled, are known in the prior art. Such systems include central controllers coupled to a plurality of readers, each of which is located at a specific door to be controlled. Authorized persons wishing to gain accesss through a door, insert magnetic cards into slots in the reader. Magnetic codings on the cards are then read and data is sent to the controller which authorizes or refuses entry and tells the reader either to keep the door locked or unlock the door.
A problem arises when communication between a remote card reader and the central controller is lost. If all access is denied during such times, peoples lives may be endangered. If open access to anyone is granted, security may be breached with no record of who was granted access during the down or degraded mode period.